A typical and common frame-enclosed overhead garage door assembly comprises a pair of vertical tracks wherein each vertical track is mounted on opposite sides of the garage door opening, extending up the sides of the opening. These tracks are parallel to each other and sometimes are curved perpendicularly at their uppermost points to extend back into the garage.
Other times, instead of using curved vertical tracks, a pair of parallel horizontal tracks which also extend back into the garage are used. Each horizontal track corresponds to one of the vertical tracks. The horizontal tracks are substantially perpendicular to and intersect the uppermost point of their respective vertical tracks.
Rollers or wheels are mounted onto the side edges of the door, typically adjacent to the corners of the door, and inserted into the tracks enabling the door to move within the tracks.
When the door is in its fully opened position, it extends back over the opening parallel to the floor. As the door is being closed, it begins to develop a downward component of force due to its weight.
To prevent the door from forcefully and rapidly closing shut under its own weight while it is in the partially open position, a counterweight is ordinarily provided in which at least one cable is connected at one end to the door and at its opposite end to a spring which is attached to the building frame or track.
The force of the spring is designed to balance approximately the weight of the door to make it easier to raise the door from its closed position and also reduce the possibility of accident should the door handle be released before it is fully open or fully closed.
Overhead garage doors are commonly found in industrial facilities and in many home and apartment garages. These doors typically have a width greater than the width of an automobile and a height greater than six feet. These doors usually have a thickness greater than approximately one inch depending on their design and type of construction. The design and construction of these overhead doors often vary. For example, some doors are completely wooden and some others are made of sheet metal mounted over a wooden or angle iron frame.
The weight of these doors can be considerable depending on their dimensions as well as the material used to make them. For example, wooden doors usually weigh substantially more than the sheet metal-type doors.
Nevertheless, overhead doors are capable of causing serious damage and injury if they are rapidly closed.
Overhead doors become even more dangerous if they either break away from their supporting upper rollers or if their rollers disengage from their respective horizontal tracks, while the door is completely or partially open, and fall. Accidents of this nature are common, and the damage and/or injury caused by these accidents are usually significant.
The only overhead garage door safety devices that presently exist are those directed towards only preventing these doors from rapidly closing downward under its own weight with great force.
The counterweight system described above, is one example of such a safety device.
Another kind of safety device for preventing overhead doors from slamming closed is disclosed in Calvagno, U.S. Pat. No. 4,520,591. The device of Calvagno is directed towards a safety lock assembly with a garage door to prevent the door from closing uncontrollably in the event the counterweight system, discussed above, fails. This device is comprised of a pivoted arm biased into a position blocking the movement of the door. The counterweight system is attached to the pivoted arm to overcome the bias. In the event of a failure in the weight supporting members, the built-in bias will move the arm into its position where further significant movement of the door is prevented.
These systems and devices, however, do not prevent overhead doors from falling and causing serious injury or damage should the supporting upper rollers fail by either breaking away from the door or by becoming disengaged from the tracks. Presently, no such safety device exists which overcomes this problem.